Boston Police Officer David Williams is carving out an interesting career path for himself: He gets fired for using excessive force or lying to investigators, takes a breather from police work, and then gets reinstated with back pay by a labor arbitrator. Nice work if you can get it. Especially in Boston, where an officer gets credit for all of those lucrative hours of overtime and details he might have worked had he had stayed out of trouble in the first place.

Last year, Boston Police Commissioner Edward Davis fired Williams after concluding that the officer choked a suspect during a 2009 arrest and lied about it to Internal Affairs investigators. Williams appealed the finding to an independent arbitrator who ruled in his favor last week. Absent court intervention, Williams can expect reinstatement and a city check for more than $150,000.

This isn’t new territory for Williams. He was fired in 1999 during the fallout over the beating and abandonment of plainclothes officer Michael Cox, who was mistaken for a shooting suspect following a high-speed pursuit. In 2005, an arbitrator overturned that termination and awarded Williams about $550,000 in foregone pay. It was a stunner considering that a civil jury years earlier had found Williams liable for beating Cox.

Arbitrators display a dangerously high tolerance for acts of violence on the part of police. In 2003, an arbitrator overturned the nine-month suspension of Officer Craig Jones, who punched a handcuffed suspect during the same high-profile Cox incident. And let’s not forget ladies’ night at the local lockup. In 1999, officer Jane Dean got hit with a nine-month suspension for striking a handcuffed prisoner. The Civil Service Commission knocked that suspension down to 10 days.

“It’s a difficult process to remove people from this job,’’ said Commissioner Davis, in what is surely one of the great understatements on local law enforcement.

A decade ago, police officers favored the Civil Service Commission when appealing their suspensions or terminations. Nowadays, they prefer to make their case to a rotating panel of independent arbitrators. And who could blame them? According to the Boston Police Department, only six of 23 arbitration cases have gone in management’s favor over the past seven years.

Policing the police is a gauzy business, especially regarding the use of force. On paper, the policy is straightforward: Officers should use the least amount of force needed to subdue a subject. Out on the street, it’s another story.

Investigators say that Williams applied a forbidden chokehold on an unruly man — off-duty corrections officer Michael O’Brien — during the 2009 fracas following a fender bender in the North End. They say that medical records clearly indicate signs of choking. So clearly, in fact, that the city paid O’Brien $1.4 million to settle a federal lawsuit.

“He [Williams] choked this guy out and lied about it,’’ said Davis. “He shouldn’t be allowed to be a police officer.’’

Arbitrator Michael Ryan sees it differently: It was the drunken accuser who lied about being choked to within an inch of his life; and medical records support Officer Williams’s version of events. As for the officer’s method of controlling the suspect, the arbitrator determined that applying a chokehold “is not the same thing as choking or strangling’’ someone.

That last point really takes your breath away.

The Internal Affairs department, meanwhile, didn’t help its cause by dragging out the investigation. For 20 years, outside analysts have been warning of the likelihood of faded memories and disappearing evidence in the event of overlong Internal Affairs investigations. In this latest case, the arbitrator noted that investigators “did nothing’’ about O’Brien’s complaint for a year and allowed nearly two years to pass before placing Williams on administrative leave.

“If the department investigated in a timely fashion, O’Brien never would have had a case in the first place or received $1.4 million in taxpayers’ money,’’ said Alan Shapiro, Williams’s attorney.

This is deeply dispiriting. If the Police Department’s version of events is true, then there is little likelihood that rogue officers will be held accountable for misdeeds. If the arbitrator is right, the public got taken for a $1.4 million ride.

Davis said the department will appeal the arbitrator’s ruling to Superior Court. But he doesn’t hold out much hope given the court’s narrow authority over labor arbitration decisions.

So let’s stay on the safe side. If Officer Williams returns, he should ride a desk. And preferably one that is bolted to the floor.

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